A mess happens when i try to unwrap my model, any idea whats causing this?
the problem is your model. You have got a lot of strange faces in the inside of your sword, and on top of the sword some vertices that are not connected while they should be. So you have to delete all the inner faces and connect the vertices that should be connected. And then add the seams and UV-unwrap the model 
In the blendfile I add, I corrected it all so you can see the difference.